Steam plays an integral role in the food processing industry for various purposes such as cooking, drying, sterilizing, packaging, etc. Since steam is energy efficient and reliable in transferring heat to food products, it is essential to check and maintain the steam quality. Steam quality in food processing industry directly affects the food and causes contamination as it is in direct contact during process operations. Steam quality in food processing industry varies as per its utilization purpose and different levels of contamination risk. Let us learn about different types of steam and their purity level in detail,
Types of Steam and Its Quality
- Plant Steam:
Plant steam is the lowest quality of steam and consists of a high amount of impurities and contaminants. The impurity level in plant steam is determined by the factors such as,
- The quality of feed water entering the steam boiler
- The amount of chemicals used in the steam boiler for the water treatment management
- TDS level, operating pressure, and other components of steam boiler operation
- Filtered Steam:
Filtered steam, also known as culinary steam, is the most utilized type of steam in food processing sector. It passes through a fine stainless steel filter, usually of five-micron pore size. The impurities from feed water treatment chemicals and cross-contamination are present in filtered steam. The amount of contaminants passing through the filter depends on the nature of the boiler problem, frequency of boiler maintenance, and the velocity of the steam.
- Clean Steam:
Clean steam is the highest level of steam quality in food processing and beverage industry. It is generated from purified water in a specific clean steam generator. Clean steam is mainly used for process operations that rely on the superior quality of products.
- Pure Steam:
Pure steam is slightly higher than clean steam in terms of purity and is largely used in pharmaceutical industries. With the increasing requirement of steam quality in food processing industry, pure steam is also used in the food and beverage processing sector.
Determining Steam Quality:
Steam quality refers to the amount of water present in the generated steam. It is also defined as dryness fraction that is measured by the following formula,
Dryness Fraction = Mass of Steam/Mass of steam + Entrained water
On the other hand, steam purity is a quantitative measure of the dissolved solids, volatiles, or other particles in the vapor remaining in the steam after the separation from the steam boiler.
Causes of Steam Contamination:
Various factors contribute to the contamination of the steam quality. Following are some of the factors that should be controlled to minimize impurity and contamination of steam.
- Chemical Usage:
The feed water quality in steam boilers has a significant impact on the efficiency of the boiler system and steam generation. Along with the components present in the feed water, further chemicals are added in boiler water treatment to reduce the possibility of corrosion, erosion, and scaling. Excess use of chemicals may affect the steam quality.
- Boiler Carryover:
Boiler carryover is not entirely steam and consists of harmful boiler treatment chemicals in the form of entrained water and foam. The two factors that mainly cause carryover in the boiler are:
- Priming:
During steam generation, some water particles are carried along with the steam. The process of formation of wet steam is known as priming. It is caused due to,
- Negligence in regular maintenance and proper water treatment
- High water level
- Operating the steam boiler below the design pressure
- Sudden steam demand
- Foaming:
Foaming is the constant formation of bubbles or foam in the steam boiler caused by the oily substances in water that reduce the surface tension in the boiler water. The greater amount of foaming leads to severe issues in steam boilers. The major contributors of foaming in steam boilers are,
- High levels of Total Dissolved Solids (TDS) in the boiler system
- Excess amount of water treatment chemicals
- Boiler water contamination from other areas of the process
- High alkalinity (>1 000 ppm)
- Cross Contamination:
Several food processing plants return condensate for reducing water, energy, and chemical utilization. As the condensate passes through the steam boiler system, it may be subjected to cross-contamination from other sources.
- Corrosion and Scaling:
Carbon dioxide and oxygen cause severe corrosion of steam/condensate pipework and boilers. As a result, corrosion products can precipitate and form deposits that contaminate steam supplies and any area using steam.
- Non-condensable gases:
Dissolved gases in feed water such as oxygen, ammonia, and carbon dioxide may lead to corrosion, reduced heat transfer, etc. in a steam boiler. It is essential to control the amount of gases in the boiler system.
Preventive Measures to Ensure Steam Quality for Food Processing Industry:
- Efficient Operation:
It is necessary to ensure hassle-free steam boiler operation. With a constant load of steam boiler and design parameters, the entrained moisture carried over within steam should be less than 2%
- Chemical Usage:
The amount of chemicals in the steam boiler should be as per the requirement and not be in excess.
- TDS Control:
TDS level must be controlled as per the water treatment guideline and at levels that minimize the effect of foaming
- Condensate assessment:
Condensate and steam sampling should be performed regularly to ensure appropriate water treatment procedures. Since steam boiler carryover is dependent on various factors, infrequent testing may not always identify the occurrence of carryover.
- Monitoring of Cross Contamination:
Cross-contamination of the steam boiler system from other sources can occur at any time and, therefore, should be monitored regularly.
Conclusion:
Rakhoh Boilers, with their 38+ years of experience, are one of the best steam boiler manufacturers in India and abroad. We provide efficient steam boilers, waste heat recovery systems, thermic fluid heaters, boiler accessories, and boiler services to over 20 process industries in 26 countries worldwide.
To learn more about our products and services, visit www.rakhoh.com